1. Field of the Invention
The present invention relates to a method of connecting packet switching networks and, more particularly, this invention relates to a method of setting up virtual connections in packet switching networks.
2. Description of the Prior Art
Various methods of connecting packet switching networks are known in the art, one such method is disclosed in German Published Application DE 41 28 938. In this method, when a pending call packet does not have a connecting path for call setup within a first packet switching network, the call packet is transmitted to a first network interface location in modified form via a second packet switching network. In addition to an address field, an address expansion field is provided in this modified call packet. The address expansion field contains address information identifying a second network interface location and an information flag indicating that the address field and address expansion field have been exchanged. The address information contained in the address field and in the address expansion field of the modified call packet are exchanged with one another at the first network interface location. A connecting path is subsequently defined within the second packet switching network to the second network interface location and the modified call packet is forwarded to that location. This connecting path is defined based on the address information now contained in the address field of the modified call packet which identifies the second network interface location. The address information contained in the address field and the address expansion field are again exchanged at the second network interface location based on the flag set in the modified call packet. A virtual connection is then set up in the first packet switching network to the called subscriber equipment based on the address information that is now contained in the address field of the modified call packet. This information identifies the called subscriber equipment.
This known method requires that the second packet switching network be capable of recognizing the "address expansion" protocol. It cannot be assumed, however, that every packet switching network is capable of recognizing and interfacing with the "address expansion" protocol. Thus, there is the need in the art for a method of creating virtual connections in packet switching networks without the requirement that the second packet switching network be capable of interfacing with a particular protocol.